[Central-Electronics] 600L Helicopter Parent SWR Trip

[George Maier]

That sounds like a good idea, Jim, thanks for passing it along.  Something I mentioned to Chris was that one of the CE designers (can't remember his call sign) told me many years ago that the 1N34's in the VSWR detector circuit have a nasty habit of going south, and causing such problems.   For some reason, I never had the relay chatter problem, so I left the wedge out to take advantage of the protection.  Sorry to hear that it bit you, Chris!!

I wonder if anyone else on the list has had a similar experience? 


73, George - W1LSB


-----Original Message-----
From: central-electronics-bounces at mailman.qth.net [mailto:central-electronics-bounces at mailman.qth.net] On Behalf Of Jim Candela
Sent: Sunday, September 23, 2018 7:23 AM
To: central-electronics at mailman.qth.net; Christopher Bowne
Subject: Re: [Central-Electronics] 600L Helicopter Parent SWR Trip

Chris,

I had the same problem with my 600L. Had a piece of wood in the relay from a prior owner.

What I did was to delay the overload relay response time. Running SSB I could see the relay moving with my voice. 

I put an electrolytic capacitor across the relay coil sufficiently large enough to stop the relay from moving with my voice. Protection still worked with a slight delay.

I cannot remember the cap value, but It was non critical. Get the polarity correct!

Jim
Wd5jko

From: Christopher Bowne
Sent: Saturday, September 22, 1:32 PM
Subject: [Central-Electronics] 600L Helicopter Parent SWR Trip
To: central-electronics at mailman.qth.net


Hello from Chris in Stonington CT. I subscribed to the list several months ago, just found a digest sent a few days ago, was in my spam bucket. Hopefully I will get more now. I have been running a 20A with a 600L that I acquired from George W1LSB a few months ago. Works great overall, but the high SWR protection trips way to often on 80/75 meters, even when transmitting into a Bird dummy load with essentially flat SWR. My coax fed inverted vee with ferrite bead common mode isolation beads at the feed point has a nominal SWR of less than 1.2 to 1 on 75/80. I have the sensitivity pot of the SWR trip circuit sent to minimum sensitivity. Looking at the circuit, I am thinking of either adding more resistance in series with the signal coming off the SWR bridge to the grid of the 12AT7 relay control tube, or swamping down the grid a bit. Any other suggestions? The amp came with a melamine wedge to lock the relay in the normal position to prevent tripping, but I don’t want to go that route, and don’t think further reduction of the small SWR present with an antenna tuner makes sense and not likely to work Chris AJ1G Stonington CT Sent from my iPhone ______________________________________________________________ Central-Electronics mailing list Home: http://mailman.qth.net/mailman/listinfo/central-electronics Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Central-Electronics at mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html

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